Instrumentation amplifier circuits are well-known in the art and are typically used to monitor the voltage signals which appear on a pair of conductors. The instrumentation amplifier outputs a voltage which represents the difference of the voltage signals appearing on the monitored conductors. The subject precision isolation amplifier performs this function by adding error correction circuitry to a basic isolation amplifier circuit to thereby produce two error-free output signals. The first of these output signals is proportional to only the longitudinal variation of the monitored conductors and is equal to one half the sum of the voltage signals appearing on those conductors. The second output signal is proportional to only the metallic signal appearing on those conductors and is proportional to the difference of the voltage signals appearing thereon.
The error correction circuit consists of a pair of up/down emitter followers and a current mirror circuit which function to selectively eliminate both the longitudinal components of the monitored voltage signals and the voltage offset generated by the basic isolation amplifier to thereby produce the aformentioned output signals in error-free fashion.